1. Field of the Invention
The present invention relates generally to monitoring and locating systems, and more specifically to a system for tracking in real time the location of individuals, pets or objects within a defined environment such as a ball park, playground, theme park or other such fixed activity environment using radio frequency identification (RFID) technology.
2. Description of the Prior Art
Tracking the location of an individual or an object or even an animal such as a domesticated animal or a pet that can move in unknown directions over a considerable range of territory presents an interesting challenge. A number of systems have been proposed which employ existing wireless communication capabilities but which tend to be cumbersome, bulky and expensive. With the advent of global positioning system (GPS) services, it has been possible to provide relatively inexpensive location systems for determining the location of a moving object. These type systems have been used, for example, on trucks to provide location information for companies that have large fleets of trucks in use at any one particular time. However, the global positioning system (GPS) has some disadvantages in that it is relatively slow in acquiring the location data and it is strongly dependent upon the target object being in an open area where it is in a line of sight position relative to at least three GPS satellites. A further disadvantage, particularly in a small, portable unit, is that the GPS receiver that must be included in a locating device requires the use of substantial electrical energy during the period in which the location information is being acquired and developed from the GPS system. Further, a small portable object locator, in addition to minimizing the use of electrical power while being subject to less than ideal orientations must also be very simple in design and economical to manufacture.
There are numerous prior art references which are directed toward the problem of locating and tracking people, objects and pets. For example, Joseph Hoshens, U.S. Pat. No. 5,461,390, teaches a system designed to track stalkers, stalkees, abducted or stolen animals or objects to which tags are attached.
The system is based on a cell phone-type network. Polling signals are sent to transceivers (repeaters) in each cell which then broadcast the polling signals to each of the tags. Each of the polled tags then interrogates a unit of a global positioning system to obtain its coordinate position. This information is then broadcast to the control center via the repeaters. Alternately, the tags can transmit signals which are triangulated by the control center data processor to obtain the tag location. The coordinates are then, in the case of a stalker, compared with the spatial coordinates of locations, permitted to the stalker or the stalker's spatial relationship to the stalkee. If the stalker is in a nonpermitted area, or too close to the stalkee, police are then notified of the fact. In the case of an abducted child, the presence of the child in a location outside a designated area would trigger a notification of the police. Alternately, the child can trigger an abduction-in-progress alarm.
J. C. Otto, et al, U.S. Pat. No. 5,870,029, teaches the location of objects or persons, e.g., a person under house arrest, within designated areas. A police car acting as a mobile transceiver is dispatched to apprehend the fugitive when he or she is outside the designated areas. A geo-positioning system is utilized to provide the necessary spatial coordinates. The mobile transceiver utilizes signal strength, ranging Doppler effects, phase shifting, radio direction, time difference of signals arrived and radio frequency ranging for determining the location of the tagged individual or object.
U.S. Pat. No. 5,883,598, to Parl, et al., teaches a location system designed to augment cellular phone or paging systems which utilizes identification tags. Each tag transmits locating signals to one or more repeaters within the cell areas. A base station relay within the cell areas receives the locating signals and transmits to the control center signals indicative of the phase and amplitude of each locating signal as received.
The above references are merely intended to be illustrative of the state of the art in locating system technologies. Most of these systems are extremely complicated and expensive to implement. While such systems may prove useful in, for example, law enforcement, fleet trucking, child abduction, and the like, a need exists for a much simpler and economical alternative for use in, for example, monitoring the location of a child within a defined environment such as a school building, sports arena, playground or theme park.